Removable dental bridge and method for making same

ABSTRACT

A PATIENT-REMOVABLE DENTAL BRIDGE INCLUDES A MALE SUPPORT MEMBER MOUNTED ON AN ABUTMENT TOOTH TO SERVE AS A BRIDGE SUPPORT, AND A FEMALE MOUNTING MEMBER EMBEDDED IN AN ARTIFICIAL TOOTH AND INCLUDING A SOCKET TO BE RELEASABLY ENGAGED WITH THE MALE MEMBER. THE MALE MEMBER IS A SOLID PIECE EXTENDING ABOUT ONE-HALF THE WIDTH AND THE ENTIRE HEIGHT OF THE ARTIFICIAL TOOTH. A NARROW AND SHALLOW NOTCH IS LOCATED IN THE TOP EDGE OF THE MALE SUPPORT MEMBER, PREFERABLY NEAR THE CORNER ADJACENT THE ABUTMENT TOOTH. A TRANSVERSE BRIDGE PIECE IN THE TOP OF THE FEMALE MEMBER FITS INTO THE NOTCH WHEN THE TWO MEMBERS ARE ENGAGED TO ACT AS A STOP AGAINST MOVEMENT OF THE ARTIFICIAL TOOTH INTO THE GUM TISSUE. A TENSION BAR DISPOSED BETWEEN THE MALE AND FEMALE MEMBERS PROVIDES PROPER TENSION BETWEEN THE TWO MEMBERS AND CAN BE ADJUSTED TO COMPENSATE FOR WEAR. THE TWO MEMBERS ARE MADE BY TRIMMING PLASTIC MALE AND FEMALE DIES INTO THE DESIRED SHAPES. THE MALE SUPPORT MEMBER IS CAST FROM THE MALE DIE, AND THE FEMALE DIE IS THEN FITTED ONTO THE CAST MALE MEMBER TO FACILITATE FORMING THE BRIDGE PIECE. THE FEMALE MOUNTING MEMBER IS THEN CAST FROM THE FEMALE DIE.

United States Patent [191 Lasky June 28, 1974 REMOVABLE DENTAL BRIDGE AND METHOD FOR MAKING SAME [76] Inventor: Mervyn C. Lasky, 1535 N.

Poinsettia PL, Hollywood, Calif. 90046 22 Filed: Feb. 22, 1973 [2]] Appl. No.: 334,729

Primary Examiizer-Robert Peshock Attorney, Agent, or Firm-Christie, Parker & Hale 57 ABSTRACT A patient-removable'dental bridge includes a male support member mounted on an abutment tooth to serve as a bridge support, and a female mounting member embedded in an artificial tooth and including a socket to be releasably engaged with the male member. The male member is a solid piece extending about one-half the width and the entire height of the artificial tooth. A narrow and shallow notch is located in the top edge of the male support member, preferably near the corner adjacent the abutment tooth. A transverse bridge piece inthe top of the female member fits into the notch when the two members are engaged to act as a stop against movement of the artificial tooth into the gum tissue. A tension bar disposed between the male and female members provides proper tension between the two members and can be adjusted to compensate for wear. The two members are made by trimming plastic male and female dies into the desired shapes. The male support member is cast from the male die, and the female die is then fitted onto the cast male member to facilitate forming the bridge piece. The female mounting member is then cast from the female die.

14 Claims, 9 Drawing Figures Pmmwwwzwm mmml SHEET 1 BF 3 REMOVABLE DENTAL BRIDGE AND METHOD FOR MAKING SAME BACKGROUND OF THE INVENTION This invention relates to dental bridges, and more particularly to a semi-fixed patient-removable bridge, and a method of making such a bridge.

There are several advantages of patient-removable dental bridges, the major advantage being that the patient can periodically remove the artificial tooth, or pontic, to cleanse the abutment tooth, the gum tissue in the area of the pontic, and the pontic itself. Conversely, fixed bridges can be a source of trouble for the patient, because food particles become trapped be tween the pontic and the surrounding gum tissue. Since the trapped food particles are virtually impossible to remove, over a period of time they decay and can cause. irritation or inflammation of the gum tissue, which eventually can cause pyorrhea and recurrent decay.

Other advantages of patient-removable bridges over fixed bridges include easy access to all teeth in the area of the pontic when the pontic is removed, and substantially simplified repair work required of the dentist if any trouble develops in the abutment teeth or pontics.

My US. Pat. No. 3,17 L202 discloses a patientremovable dental bridge which generally includes a U shaped male support member rigidly secured to an abutment tooth. A female mounting member embedded in the artificial tooth has a U-shaped socket releasably fitted over the male member to hold the artificial tooth next to the abutment tooth. Although the bridge disclosed in my patent has proved to be successful in use, it has several disadvantages which are overcome by the improved bridge attachment of the present invention. It will become clear from the description below that the attachment of this invention is substantially stronger than my previous bridge in resisting the stress exerted on the bridge members during use. This substantially prevents breakage of the attachment members during use. The present dental bridge also is simpler in construction than the previous bridge, which reduces manufacturing time and costs, as well as reducing the chances of manufacturing bridge attachments susceptible of premature breakage.

SUMMARY OF THE INVENTION Briefly, the dental bridge attachment of this invention includes a male support member to be mounted on an abutment tooth to serve as a bridge support, and a female mounting member rigidly secured to a pontic and having a socket shaped to be releasably fitted on the male member. The male member is a solid piece extending mesio-distally from the abutment tooth preferably for about one-half the width of the pontic. The solid piece has a pair of spaced apart. upright first and second edges which extend occluso-gingivally substantially the entire height of the pontic. and a top edge extending between the first and second edges. The top edge traverses a major portion of the width of the male member, with the remaining portion of the top edge being recessed to form a narrow, relatively shallow notch in the top of the male member. The depth of the notch extends for a minor portion of the height of the male member.

The socket formed by the female member includes spaced apart lingual and facial surfaces to be engaged with opposite sides of the male member, and a bridge piece connecting the tops of the lingual and facial surfaces. The bridge piece is shaped to match the contour of the notch in the male member, and makes a tight fit in the notch when the male and female members are releasably secured to each other.

In use, the cooperating notch and bridge piece act as an occlusal stop to prevent movement of the pontic into the gum tissue. The male member provides a relatively long and wide solid support for the pontic, which substantially prevents breakage of the attachment members when compared with prior art removable bridges. H

In a preferred form of the invention, the notch is near the top corner of the male member adjacent the abutment tooth. This reduces substantially the stress exerted on the attachment members during use, because the leverage acting on the bridge piece during use is minimized due to the support provided for the bridge piece by the adjacent abutment tooth.

Preferably, the male member includes an upright shoulder located remote from the abutment tooth. The female member includes an elongated channel which engages the shoulder when the two members are connected. This construction provides added stability for the attachment, and keeps the teeth from drifting apart mesio-distally during use.

A tension bar preferably is disposed between the male and female members when the pontic is in place to provide proper tension between the two members. The tension bar can be adjusted to compensate for wear between the two members.

The preferred method of making the dental bridge includes trimming a solid plastic, or metal, piece to form a male die in the shape of the male support memher, and trimming a socket'shaped plastic, or metal, piece to form a female die in the shape of the female mounting member. The male and female dies preferably are plastic pieces having a width about one-half that of the pontic and a height greater than the pontic. The male support member is cast first from the trimmeddown male die. The female die is then fitted over the cast male member to facilitate shaping the outer dimensions of the female die and forming the bridge piece. The female mounting member is then cast from the female die.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be more fully understood by referring to the following detailed description and the accompanying drawings in which:

FIG. I is an exploded elevation view. partly in sec tion, showing male and female attachment members of a prior art removable bridge;

FIG. 2 is an exploded elevation view, partly in section. showing male and female attachment members of a removable bridge according to this invention;

FIG. 3 is a schematic exploded perspective view showing the detailed construction of the male and female attachment members of this invention;

FIG. 4 is a schematic perspective view showing the male and female members of FIG. 3 in their engaged position, and also showing a tension bar on the lingual side of the attachment;

FIG. 5 is a schematic perspective view of the male and female members engaged in an alternate configuration in which the tension bar is located at the end ofthe attachment remote from the abutment tooth;

FIG. 6 is an exploded perspective view showing male and female dies to be used in forming the attachment members of this invention;

FlG. 7 is a schematic perspective view showing two male members releasably engaged with a double female mounting member, and also showing a U-shaped tension bar at the interface between the two male mem bers;

HO. 8 is a schematic elevation view taken on line 7-7 of FIG. 7; and

FIG. 9 is a schematic perspective view showing an alternate configuration of the attachment in FIG. 7 in which a pair of tension bars are located on the lingual side of the attachment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a prior art patient-removable bridge 10 of the type disclosed in my U.S. Pat. No. 3,l7l.202 mounts a pair of side-by-side artificial teeth or pontics (represented schematically at 12) in the space between a right natural tooth abutment l4 and a left natural tooth abutment 16. The removable bridge includes a generally U-shaped right male support member 18 soldered to an inlay 20 in abutment tooth 14, and a generally U-shaped left male support member 22 soldered to an inlay 24 in the left abutment tooth. Each male member includes a narrow upright leg 26 at the end thereof remote from the abutment tooth. Leg 26 is spaced from an attachment portion 28 of the male member by a narrow, longitudinally extending slot 30.

Bridge 10 also includes a pair of side-by-side right and left female mounting members 32 and 34, respectively. A longitudinally extending bridge member 36 interconnects the adjacent upper corners of the two femalemembers. Each female member is embedded in a respective pontic l2, and each member forms a U- shaped socket adapted to slip releasably over a corresponding one of the male members to mount the two pontics in the space between the right and left abutment teeth. Each female member includes opposed; narrow. elongated recessed faces 38 to be engaged in slot 28 of the male member. and inwardly extending abutment ridges 40 at the bottom of the recess on the lingual and facial sides of the female members. Ridges 40 rest on the bottom of slot 28 to limit gingival movement of the bridge.

There are several disadvantages of the prior art bridge 10 which are overcome by the present invention. For example. leg 26 of the male member is relatively thin. and a substantial amount of leverage is exerted on it during use because it is located at the furthest remote point from the members point of support on the abutment tooth. Because of these factors. leg 26 is prone to breakage. usually at its base. due to the constant force exerted on it during use.

The prior art male member also requires the use of extreme care during manufacture. There is a likelihood that leg 26 sometimes will be ground too thin. thereby increasing the chances ofbreakage. There is also a likelihood that slot 30 will be ground too deep, leaving too thin a bridge 42 at the base of the member between leg 26 and attachment portion 28. Substantial stress is concentrated at bridge 42 during use. because forces from chewing are transferred to the bottom of slot 30 by abutment ridges of the female member, and because of the leverage due to the remote location of bridge 42 from the male members point of support on the abutment tooth. Because of this stress concentration. there is an increased chance that the member will break at the base ofslot 30 in the event bridge 42 is ground too thin. To prevent such breakage requires extreme care during grinding which, in turn, makes the manufacturing process for the attachment costly, time consuming. and wasteful of material.

The problems associated with prior art bridges 10 are overcome by a removable bridge or attachment members 44 shown in FlGS. 2 and 3. The finished attachment members 44 are made by a process described in detail below. Bridge 10 includes right and left male support members 46 and 48 soldered to inlays in right and left abutment teeth 50 and 52, respectively. Each male member is a solid piece extending mesio-distally from its corresponding abutment tooth for about onehalf the width of a pontic 54 to be mounted on the male member. The male member also extends occlusogingivally the entire height of the pontic. The male member is generally rectangular, and includes a planar top edge 56 extending between a pair of longitudinally spaced apart, upright first and second edges 58 and 60, respectively, which extend occluso-gingivally for the entire height of the pontic. First upright edge 58 is located remote from the corresponding abutment tooth of the male member. and second upright edge 60 is attached to the abutment tooth. Top edge 56 traverses a major portion of the width of the male member, and a narrow. relatively shallow notch 62 is located in a minor portion of top edge 56. The depth of notch 62 extends for a relatively minor portion of the height of the male member so that a substantial amount of material provided by the solid male member can provide good means of support below the notch for the pontic to be releasably engaged with the male member. Preferably, the depth of the notch extends only about 10 percent to 30 percent of the maximum height.

Each notch 62 preferably is located near the top corner of the male member adjacent the corresponding abutment tooth. The purpose of this preferred construction will be described in greater detail below.

Each male member also includes a vertically extending, elongated right-angle shoulder 64 continuous with the first upright edge of the member continuously for the full height ofthe member. Each shoulder 64 preferably is located on the lingual side of the attachment.

Bridge 44 also includes spaced apart right and left fe male mounting members 66 and 68, respectively, rigidl interconnected at their adjacent top corners by a longitudinally extending. elongated bridge member 70. Female members 66 and 68 are embedded in corresponding artificial teeth or pontics 54, and each is in the form of a socket adapted to be releasably engaged with respective male members 46 and 48.

Each female member preferably includes an upright facial wall surface 72 spaced facio-lingually from an upright lingual all surface 74. An end wall 76 at the remote end of the member from the abutment tooth connects surfaces 72 and 74. Lingual surface '74 in cludes an otnuaidly projecting right-angle channel 78 shaped to match the contour of shoulder 64 of the male member.

Surfaces 72 and 74 and end wall 76 extend the full height of the female member to form a socket adapted to make'asnug, releasable fit over the male support member. A transverse right angle bridge piece 80 interconnects the top corners of facial and lingual surfaces 72 and 74 at the end of the female member adjacent the abutment tooth. Bridge piece 80 is shaped to fit the contour of notch 62.

In use, when either female member is mounted on its corresponding male member (only male member 46 and female member 66 are illustrated in FIGS. 3, 4 and 5), bridge piece 80 seats in notch 62 to provide an occlusal stop preventing further gingival movement of the female member relative to the male member. Shoulder 64 interlocks with channel 78 when the two members are engaged to provide additional stability for the bridge, and to keep the pontics from drifting mesiodistally.

Bridge 44 provides substantial advantages over the prior art bridge shown in FIG. 1. Male member 46 is a substantially solid piece which eliminates the narrow leg 26, slot 30, and bridge portion 42 of the prior art male member. This substantially eliminates the chances of breakage, and also makes it much easier to fabricate the male member when compared with the prior art bridge. Further, the interlocking notch 62 and bridge piece 80 preferably are located adjacent the natural tooth support. This minimizes the leverage exerted at the point of contact between the two members during use, and thereby reduces the chance that breakage willoccur duringthe life of the attachment.

A further advantage of bridge 44 is that the male and female members can be fitted into a shorter space mesio-distally than is possible with the prior art bridge shown in FIG. I. Generally speaking, two male members and two cooperating female members are used in a bridge, whether the bridge includes one or more artificial teeth. Since leg 26 of each prior art male member shown in FIG. I must be sufficiently wide to reduce the chances of breakage, the ability of the prior art bridge to fit into narrow spaces occupied by a single artificial tooth is substantially limited. The present bridge eliminates this requirement, and a space as narrow as 7 mm. can be fitted with a two-part bridge attachment 44.

In the removable bridge attachment shown in FIG. 4, a vertically disposed narrow tension bar 82 is disposed between a the lingual surface of shoulder 64 and the inner surface of channel 78. An exterior bottom portion 84 of the tension bar is bent back on itself adjacent the outer surface of channel 78. The bar is bent slightly by a mandrel (not shown) inserted in the interior of the female member so the bar applies tension between the cooperating male and female members and produces a tight releasable fit between the two members. The space left at the bottom of the tension bar is filled with self-curing acrylic resin plastic. and the tension bar is held in place by such self-curing plastic around the bent end of the bar. The self-curing plastic is easily removable in the event the tension bar needs replacement.

The tension bar compensates for wear between the cooperating surfaces of the male and female members. If the tension on the bar needs to be increased due to wear, the female member simply is removed, and the mandrel inserted into the female member to bend the tension bar sufficiently to increase its tension.

FIG. 5 shows an alternate configuration of the attachment in which a tension bar 85 is disposed between second edge 58 of the male member and the interiorsurface of end wall 76 of the female member.

Referring to FIG. 6, attachment members 44 are made by starting with a solid male die member 86, and a socket-shaped female die member 87, both of which are made of a material which can be easily trimmed down to the shape of the finished male and female mounting members 46 and 66, respectively. Preferably, the male and female die members are made of plastic, rather than metal, such as gold, thereby facilitating ease of trimming the members and preventing waste of expensive material. However, the die members can be made of metal, if so desired.

FIG. 6 shows the male and female die members in their initial condition as they are sold to the dentist in preparation for his making the attachments. The male and female die members are the same width and thickness as the finished male support member 46 and tinished female mounting member 66, respectively. The

male die member includes a shoulder the same size as shoulder '58, and the female'member includes a channel the same size as channel 78. The top corner of the male die member does not include notch 62, and the top corner of the female die member does not include bridge piece 80, because the notch and bridge piece will be added later by the dentist after the occlusal surfaces of the male and female die members have been ground to occlusion with the teeth of the opposite jaw.

The finished bridge attachments usually are mounted with the shoulder 58 and channel 78 projecting toward the lingual side of the patients mouth. One advantage of die members 86 and 87 is their ability to serve as dies for either the right or left side of the bridge attachment simply by placing them right-side-up, or by inverting them, so that the shoulder and channel are kept on the lingual side.

The first step in forming the bridge attachments is to construct a stone model of the patients upper and lower jaws from impressions thereof so that the proper size and orientation of the attachment members can be obtained.

The female die members are mounted between the abutment teeth on the stone model, and mandrels (not shown) are then-used for paralleling the female die members. A longitudinally extending body of selfcuring plastic material is then formed between the adjacent edges of the two female die members to form a bar, such as bridge member shown in FIG. 2, for attaching the two female die members to hold them in their paralleled position. The female die members are then trimmed down to form dies having the shape which properly fits the patients bite as determined from the stone model. Notches 88 (shown in phanton line in FIG. 5) are then cut in the corner of each female die member to serve as means for later adding occlusal stop t0 the bridge attachment.

The resulting female dies are then removed from the stone model, and male die members 86 are ground gingivally and occlusally to match the contour of the previously ground female dies. A separate notch 89 (shown in phantom line in FIG. 5) is also cut in the top comer of each die to match the notch of the cooperating female die.

The male die is then used to form a mold for casting the finished male support member 46 from metal such as gold. The cast male members are soldered to their respective abutment restorations, and are automatically paralleled with the aid of the female dies. If the indirect method of casting abutment restorations is preferred, male dies 46 can be cast with the restorations, eliminating soldering.

The female dies are fitted over their respective cast male support members. (In the original forming of each female die, a groove is provided between the male and female dies to accommodate the tension bar.) A body of self-curing plastic is then added to the notched portions of the male member and the female die to interconnect the opposite sides of the female die and form the die for bridge piece 80. The remainder of the desired occlusal surface of the pontic also is added in plastic or wax. The female dies are then removed from the male support members, and are used to form a mold for casting the finished female mounting members which are then secured to pontics 54.

One advantage of this method of making the bridge attachments is that the original die members can be supplied in plastic patterns enabling the dentist or tech nician to cast his own attachments in any desired metal. This provides a saving of time and materials, because the preparatory work is done in plastics and wax. On the other hand, my previous bridge attachments shown in FIG. 1 cannot easily be manufactured by this method, primarily because leg 26 of the male member is too narrow, and therefore is difficult to cast without being so brittle that it will break easily. To avoid breakage of the male members, they would have to be cast in such large pieces that they are virtually of little practical use for most patients.

FIGS. 7 and 8 schematically illustrate a removable bridge attachment 90 especially designed to mount a single artificial tooth. The attachment includes right and left male members 91 and 92 identical in construction to male support members 46 and 48. Male mem-' bers 91 and 92 are secured to inlays (not shown) in adjacent natural tooth abutments (not shown) in a manner identical to male support members 46 and 48.

Bridge 90 also includes a pre-paralleled double female mounting member 94 to be embedded in a single pontic (not shown) and adapted to releasably fit over the two male members to hold the pontic in place. The double female member includes an elongated upright facial surface 96 adapted to abut against the facial surfaces of the male members, and a lingual surface 98 spaced facio-lingually from the facial surface 96 and adapted to abut against the lingual surfaces of the male members. Lingual and facial surfaces 96 and 98 are parallel to each other and extend mesio-distally for-a major portion ofthe width of the pontic. An outwardly projecting channel 100 is formed in the intermediate portion of lingual surface 98 to accommodate both lingual shoulders of the two male members. An internal transverse center wall 102 divides the female member in half. The top right and left corners of the double female member also include transverse bridge pieces 104 and 106, respectively, adapted to seat in the corner notches of the two male members.

A U-shaped tension bar 108 applies tension to the cooperating male and female members of bridge 90. The tension applying legs of tension bar 108 are disposed between the proximal ends of the two male members and the opposed surfaces of center wall 102.

FIG. 8 shows an alternate bridge attachment 110 which is similar to bridge 90, except that tension bar 108 is replaced by a pair of side-by-side right and left tension bars 112 and 114 on the lingual side of the attachment. In bridge attachment 110, the lower exterior portions of the tension bars are bent back, as described above for tension bar 82, to apply tension in compensating for wear between the bridge members.

Bridge attachment 88 occupies less space faciolingually than bridge 110, because U-shaped tension bar 102 is located completely internally in the attachment. Accordingly, bridge is used in instances where a tooth is so narrow that there is insufficient space to accommodate the bent back portions of the tension bars in attachment 110.

Thus, the removable bridge of this invention has improved strength, and the ability to resist breakage when compared with known prior art removable dental bridges. Moreover, the present bridge attachment is simple in configuration, which reduces fabrication time and costs.

I claim:

1. A patient-removable dental bridge system for removably mounting a pontic, the system comprising a male supporting member affixed to an abutment tooth to serve as a bridge support,

the male member being a solid piece extending mesio-distally from the abutment tooth for about one-half the width of the pontic,

the male member having a pair of spaced apart, up-

right first and second edges which extend occlusogingivally for a major portion of the height of the pontic, and a topedge extending mesio-distally between the first and second edges of the male memher,

the top edge having a first portion extending from the first upright edge toward the second upright edge and traversing a major portion of the width of the male member, and a second portion which is recessed to form a relatively shallow notch in the top edge of the male member adjacent the abutment tooth,

the depth of the notch extending for a minor portion of the height of the male member, and

a female member rigidly secured to the pontic, the

female member comprising a socket shaped to be releasably mounted on the male member,

the socket being formed by spaced apart lingual and facial surfaces to be engaged with opposite sides of the male member, and a bridge piece connecting the tops of the lingual and facial surfaces and being shaped to match the size and shape of the notch in the male member,

the bridge piece being positioned relative to the male member to make a tight fit in the notch of the male member when the female member is mounted on the male member so the bridge piece and notch cooperate to prevent relative movement mesiodistally and occluso-gingivally between the pontic and the male members.

2. Apparatus according to claim 1 in which the first 5 upright edge is spaced remote from the abutment tooth and extends the entire height of the male member, the second upright edge is adjacent the abutment tooth and extends upwardly from the gum tissue for a major portion of the height of the male member, and the first portion of the top edge intersects the first upright edge and extends toward the second upright edge for a major portion of the width of the member, said notch being formed by the second portion of the top edge at the upper corner of the male member adjacent the abutment tooth.

3. Apparatus according to claim 1 including a shoulder continuous with the first upright edge of the male member, and in which one of the said surfaces of the female members includes a channel projecting away from the opposite surface thereof to match the contour of the shoulder of the male member so the channel can be releasably fitted over the shoulder to interlock the male and female members.

4. Apparatus according to claim 1 including a tension bar between the male member and the socket of the female member.

5. Apparatus according to claim 1 in which the female member includes an upright end wall connecting the facial and lingual surfaces thereof, the end wall being spaced from the first upright edge of the male member when the female member is secured to the male member, and an elongated tension bar in the space between the first upright edge of the male member and the end wall of the female member to compensate for wear between the engaging surfaces of the two members.

6. Apparatus according to claim 4 in which the upright face of the shoulder is spaced from the inner face of the channel, and including an elongated tension bar in the space between the shoulder and channel to compensate for wear between the engaging surfaces of the two members.

7. A patient-removable dental bridge attachment for removably mounting a single pontic, the attachment comprising a right male supporting member to be mounted on a right abutment tooth to serve as a bridge support,

a left male supporting member to be mounted on a left abutment tooth to serve as a bridge support, each male member being a solid piece extending mesio-distally from its respective abutment tooth for about one-half the width of the pontic,

each male member further having a pair of spaced apart first and second upright edges which extend occluso-gingivally for a major portion of the height of the pontic, and a top edge extending mesiodistally between the first and second upright edges of the male member,

each top edge having a first portion extending from the first upright edge toward the second upright edge and traversing a major portion of the width of the male member, and a second portion which is recessed to form a relatively shallow notch in the top edge of each male member,

the depth of each notch extending for a minor portion of the height of the male member,

the two male members being positioned relative to each other such that the first upright edges thereof are disposed adjacent one another and the second upright edges thereof are disposed remote from one another so the notched portions thereof are located remote from one another, and

a double female member embedded in the pontic, the female member comprising a right socket shaped to be releasably fitted on the right male member, and a left socket shaped to be releasably fitted on the left male member,

the sockets being formed by respective spaced apart lingual and facial surfaces to be engaged with opposite sides of the male members,

the lingual and facial surfaces extending a major portion of the width of the pontic, and

right and left bridge pieces connecting the tops of the lingual and facial surfaces of the right and left sockets, respectively,

the right and left bridge pieces being shaped to match the size and shape of the notches formed in the right and left male members, respectively,

each bridge piece being positioned relative to its corresponding male member to make a tight fit in its respective notch when the double female member is mounted on the two male members so the bridge pieces and notches cooperate to prevent relative movement mesio-distally and occluso-gingivally between the pontic and the male members.

8. Apparatus according to claim 7 in which the first upright edge of each male member is spaced remote from its corresponding abutment. tooth and extends substantially the entire height of the male member, the second upright edge of each male member is adjacent its corresponding abutment tooth and extends upwardly from the gum tissue for a major portion of the height of the male member, and the first portion of the top edge of each male member intersects its corresponding first upright edge and extends toward its corresponding second upright edge for a major portion of the width of the member, the notch in each male member being formed by the second portion of the top edge at the upper corner of the male member adjacent its corresponding abutment tooth.

9. Apparatus according to claim 7 including a separate shoulder extending along the first upright edge of each male member, both shoulders projecting faciolingually in the same direction, and in which one of said surfaces of the double female member includes a chan nel projecting away from the opposite surface thereof in the same direction as the shoulders of the male members to match the contour of both shoulders so the channel can be 'releasably fitted over the shoulders to interlock the male and female members.

10. Apparatus according to claim 7 in which the double female member includes an interior transverse wall interconnecting the lingual and facial surfaces thereof substantially along the mid-point of the female member to form a pair of substantially L-shaped sockets adapted to fit over the respective-male members.

llll. Apparatus according to claim 10 in which the second upright edge of each male: member is spaced from the interconnecting transverse wall of the female member, and including an elongated tension bar in each of said spaces to compensate for wear between the engaging surface of the two members.

12. Apparatus according to claim 9 in which the shoulder of each male member is spaced inwardly from the inner wall surface of the channel, and including a separate elongated tension bar in the space between the shoulder of each male member and the inner surface of the channel to compensate for wear between the two members.

113. For use in making a removable dental bridge which includes a male support member to be mounted .on an abutment tooth to serve as a bridge support, and a female mounting member to be rigidly secured to a pontic, the female member including a socket shaped to be releasably fitted over the male support member to removably mount the pontic adjacent the abutment tooth,

a male die member comprising a solid piece having a width about one-half that of the pontic and a height greater than that of the pontic, the width of the male die member being defined by a pair of longitudinally spaced apart and substantially parallel first and second edges which extend for a distance greater than the height of the pontic, the thickness male support member having a height substantially equal to the height of the pontic, and

a female die member comprising a socket shaped to be releasably fitted over the male die member, the female die member having a height greater than that of the pontic, with the socket thereof being formed by laterally spaced apart first and second wall surfaces to be engaged with the opposed first and second wall surfaces of the male die member, and a channel projecting away from the first wall surface thereof to match the contour of the shoulder on the male die member so the channel can be releasably fitted over the shoulder to interlock the two die members to prevent relative movement mesio-distally between the male and female die members, the female die member also being made I of a material which can be easily trimmed down to form a die for said female mounting member having a height substantially equal to that of the pontic.

14. Apparatus according to claim 13 in which the male and female die members are made of plastic.

jg gg UNITED STATES PATENT OAFFICE CERTIFICATE OF CORRECTION Patent No. ,g41 Dated June 28 1974 MERVYN C. LASKY Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 6, line 66, ."corner of each die should read corner of each male die Col. 8, line 62, "members" should read member Claim 1 Col. 10, line 58, "surface" should read surfaces Claim 11 Signed and sealed this 29th day of October 197 (SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

